The present application relates to the use of an organosiloxane bearing at least one ultraviolet-absorbing group in, and for the preparation of, a cosmetic or dermatological composition as an agent for protecting the colour of artificially coloured keratin fibres against the effects of UV radiation, in particular solar radiation.
It has been known for a long time that washing agents and light in particular have a tendency to attack the artificial colour of dyed hair. The hair colour thus obtained after a dyeing treatment gradually fades or turns to less attractive or desirable shades.
It has thus been found necessary to protect the colour of keratin fibres which have undergone a dyeing treatment, and in particular the colour of hair, and to substantially reduce the degradations associated with the action of external agents, in particular UV radiation and more particularly solar radiation.
The inventors have discovered, and this forms the subject of the invention, that screening silicones bearing ultraviolet-absorbing groups preserve, surprisingly, the colour of artificially coloured keratin fibres and in particular the hair, by substantially reducing the degradations associated with the action of UV radiation, in particular the action of solar radiation.
The subject of the invention is therefore the use of an organosiloxane bearing at least one ultraviolet-absorbing group in, and for the preparation of, a cosmetic or dermatological composition as an agent for protecting the colour of artificially coloured keratin fibres against the harmful effects of UV radiation, in particular solar radiation.
Other subjects will become apparent on reading the description and the examples which follow.
The organosiloxanes bearing ultraviolet-absorbing groups, which are used according to the invention, preferably contain in their molecule at least one unit of formula: 
in which:
Rxe2x80x2 denotes a saturated or unsaturated C1-C30 hydrocarbon group, a C1-C8 halogenated hydrocarbon group, an aromatic hydrocarbon group or a trimethylsiloxy group;
a=1 or 2;
T=xe2x80x94Exe2x80x94U where E represents a saturated or unsaturated, linear or branched aliphatic divalent hydrocarbon radical having at least 2 carbon atoms and optionally containing one or more oxygen atoms, or alternatively an aromatic group, and U represents the residue of a molecule which screens ultraviolet radiation.
In addition to the units of formula (I), the polyorganosiloxane may contain units of formula (II) and/or units of formula (III):
Rxe2x80x2bxe2x80x94Sixe2x80x94O(4xe2x88x92b)/2xe2x80x83xe2x80x83(II)

in which:
Rxe2x80x2 and a have the same meanings as in formula (I);
b=1,2 or 3;
Z=xe2x80x94Oxe2x80x94U, U having the same meaning as in formula (I).
As hydrocarbon group, mention may be made of C1-C30 alkyl, C2-C30 alkenyl or cycloalkyl radicals or aromatic radicals such as phenyl or toluyl.
As halogenated hydrocarbon group, mention may be made of the 3,3,3-trifluoropropyl radical.
In the organopolysiloxanes in accordance with the invention, comprising units of formula (I) and optionally units of formula (II) and/or of formula (III), preferably, at least 40%, in numerical terms, of the radicals Rxe2x80x2 are methyl radicals. The total number of units (I), (II) and (III) is preferably less than or equal to 250 and ranges in particular from 2 to 50.
U preferably represents one of the following residues:
benzylidenecamphor optionally substituted on the benzene ring with hydroxyl or C1-C8 alkyl or alkoxy radicals;
di(C1-C8)alkyl benzalmalonate optionally substituted on the benzene ring with hydroxyl or C1-C8 alkyl or alkoxy radicals;
2-(2xe2x80x2-hydroxyphenyl)benzotriazole optionally bearing, on one of the aromatic rings, C1-C8 alkyl or C2-C8 alkenyl, halogen, alkoxy, carboxyl, hydroxyl, amino or tetraalkylpiperidyl substituents;
dibenzoylmethane optionally bearing C1-C8 alkyl or alkoxy or hydroxyl radicals;
benzophenone optionally bearing C1-C8 alkyl or alkoxy or hydroxyl radicals;
benzoate substituted with hydroxyl, C1-C6 alkoxy, amino or mono- or di(C1-C6 alkyl)amino radicals;
cinnamate optionally bearing hydroxyl, C1-C6 alkyl or alkoxy, amino or mono- or di(C1-C6 alkyl)amino radicals;
bis- or tris(phenylacrylate) optionally substituted with hydroxyl or C1-C4 alkoxy radicals.
These organopolysiloxanes bearing ultraviolet-absorbing groups are described in particular in European patent applications Nos. 0,335,777, 0,305,059, 0,392,882, 0,392,883, 0,388,218, 0,350,314, 0,383,655, 0,389,337, 0,709,080 and 0,538,431, in International patent application WO 92/20690, in French patent applications Nos. 2,550,787 and 2,657,351 and in American patents U.S. Pat. Nos. 4,696,969, 4,554,369, 4,562,278, 3,513,184 and 4,859,759, the disclosures of which are specifically incorporated by reference herein.
Particularly preferred screening silicones of the invention are chosen from those containing a benzotriazole function, which correspond to the following formulae: 
in which in formulae (1) and (2):
R, which may be identical or different, are chosen from C1-C10 alkyl, phenyl and 3,3,3-trifluoropropyl radicals, at least 80%, in numerical terms, of the radicals R being methyl,
B, which may be identical or different, are chosen from radicals R and the radical A,
r is an integer ranging from 0 to 50, and s is an integer ranging from 0 to 20, and if s=0, at least one of the two symbols B denotes A,
u is an integer ranging from 1 to 6, and t is an integer ranging from 0 to 10, it being understood that t+u is equal to or greater than 3,
and the symbol A denotes a monovalent radical linked directly to a silicon atom and corresponding to formula (3) below: 
in which
Y, which may be identical or different, are chosen from C1-C8 alkyl radicals, halogens and C1-C4 alkoxy radicals, it being understood that, in the latter case, two adjacent Y groups of the same aromatic ring may together form an alkylidenedioxy group in which the alkylidene group contains from 1 to 2 carbon atoms,
X represents O or NH,
Zxe2x80x2 represents hydrogen or a C1-C4 alkyl radical,
n is an integer ranging from 0 to 3,
m is 0 or 1,
p represents an integer ranging from 1 to 10.
As emerges from formula (3), given above, attachment of the chain unit xe2x80x94(X)mxe2x80x94(CH2)pxe2x80x94CH(Zxe2x80x2)xe2x80x94CH2xe2x80x94 to the benzotriazole moiety, which thus ensures connection of the said benzotriazole moiety to the silicon atom of the silicon-containing chain, may, according to the present invention, take place in any of the available positions of the two aromatic rings of the benzotriazole: 
This attachment preferably takes place in position 3, 4, 5 (aromatic ring bearing the hydroxyl function) or 4xe2x80x2 (benzene ring adjacent to the triazole ring) and, even more preferably, in position 3, 4 or 5. In a preferred embodiment of the invention, the attachment takes place in position 3.
Similarly, the substituent moiety or moieties Y may be attached in any of the other available positions on the benzotriazole. However, this attachment preferably takes place in position 3,4,4xe2x80x2, 5 and/or 6. In a preferred embodiment of the invention, attachment of the moiety Y takes place in position 5.
In the above formulae (1) and (2), the alkyl radicals may be linear or branched and chosen in particular from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-amyl, isoamyl, neopentyl, n-hexyl, n-heptyl, n-octyl, 2-ethylhexyl and tert-octyl radicals. The preferred alkyl radicals R according to the invention are methyl, ethyl, propyl, n-butyl, n-octyl and 2-ethyhexyl radicals. Even more preferably, the radicals R are all methyl radicals.
These screening silicones are described, along with the process for their synthesis, in application EP-A-0,392,883 and in application WO 94/06404, the disclosures of which are specifically incorporated by reference herein.
Among the compounds of formula (1) or (2) above, it is preferred to use those corresponding to formula (1), that is to say diorganosiloxanes with a short linear chain.
Among the compounds of formula (1) above, it is preferred to use those in which the radicals B are both radicals R.
Among the linear diorganosiloxanes falling within the scope of the present invention, random derivatives or derivatives with well-defined blocks having at least one and even more preferably all of the following characteristics:
B is a radical R,
R is alkyl and even more preferably is methyl,
r ranges from 0 to 15; s ranges from 1 to 10,
n is non-zero and is preferably equal to 1, and Y is then chosen from methyl, tert-butyl and C1-C4 alkoxy,
Zxe2x80x2 is hydrogen or methyl,
m=0 or [m=1 and X=O],
p is equal to 1, are more particularly preferred.
One family of compounds which is particularly suitable for the invention is that defined by the general formula (4) below: 
with 0xe2x89xa6rxe2x89xa610,
1xe2x89xa6sxe2x89xa610,
and where D represents the divalent radical: 
In a particularly preferred embodiment of the invention, the benzotriazole silicone is the compound (referred to hereinbelow as compound (c)) corresponding to the following formula: 
Another family of screening silicones which is particularly preferred comprises benzalmalonate silicones containing at least some units corresponding to one of the two formulae (5) and (6) below: 
in which:
M denotes a group having the structure: 
Mxe2x80x2 denotes a group having the structure: 
the other units of the silicone which are present having the structure:
Qdxe2x80x94Sixe2x80x94O(4xe2x88x92d)/2xe2x80x83xe2x80x83(7)
where Rxe2x80x3, which may be identical or different, denote an aryl or C1-C8 alkyl radical; W, which may be identical or different, denote a hydrogen or a C1-C5 alkyl radical; Rxe2x80x2xe2x80x3, which may be identical or different, denote a hydrogen or a C1-C5 alkyl radical or a radical OW; Rxe2x80x3xe2x80x3, which may be identical or different, denote denotes a C1-C5 alkyl group; Q, which may be identical or different, denote a hydrogen, a monovalent C1-C8 hydrocarbon radical or a halogenated hydrocarbon group: c is equal to 0, 1 or 2; d is equal to 0, 1, 2 or 3 and n ranges from 1 to 6; with the proviso that the groupxe2x80x94Mxe2x80x94Oxe2x80x94 or xe2x80x94Mxe2x80x2xe2x80x94Oxe2x80x94 is connected to the aromatic ring in a meta or para position relative to the group:
xe2x80x94CHxe2x95x90Cxe2x80x94[C(O)ORxe2x80x3xe2x80x3]2
and with the proviso that the two groups Rxe2x80x2xe2x80x3 occupy the other remaining positions on the aromatic ring.
These screening silicones are described, along with processes for their preparation, in patent applications EP-A-0,392,882, EP-0,538,431, EP-A-0,709,080 and WO92/20690, the disclosures of which are specifically incorporated by reference herein.
In a particularly preferred embodiment of the invention, one family of compounds which is particularly desired is that defined by the benzalmalonate silicones chosen from:
(i) silicones corresponding to formula (8) below: 
in which:
Vxe2x80x21 denotes a group having the structure: 
V1, which may be identical or different, denote CH3 or Vxe2x80x21;
(ii) silicones corresponding to formula (9) below: 
in which:
Vxe2x80x22 denotes a group having the structure: 
V2, which may be identical or different, denote CH3 or Vxe2x80x22;
(iii) mixtures thereof;
with 0xe2x89xa6txe2x89xa6100 and 0xe2x89xa6uxe2x89xa620, with the proviso that:
when V1=Vxe2x80x21 and/or V2=Vxe2x80x22 then u=0; and
when V1=CH3 and/or V2=CH3 then 1xe2x89xa6uxe2x89xa620.
The screening organosiloxanes of the invention are preferably used in amounts equal to at least 0.01% by weight and generally ranging from 0.1 to 20% by weight and more particularly from 0.1 to 10% by weight relative to the weight of the composition intended to be applied to the naturally or artificially coloured keratin fibres.
The compositions intended to be applied to the dyed keratin fibres in accordance with the invention may be in the form of an oily, alcoholic or aqueous-alcoholic lotion, in the form of an emulsion or in the form of an aqueous or aqueous-alcoholic dispersion.
When the compositions constitute oily lotions, they contain, besides the organosiloxane bearing an ultraviolet-absorbing group, mineral, plant, animal or synthetic oils and more particularly isoparaffins or silicone oils with a linear or cyclic structure, such as polyalkylsiloxanes, polyarylsiloxanes, polyalkylarlysiloxanes or polyorganosiloxanes modified with non-chromophoric organofunctional groups.
The oily compositions may also contain waxes, resins or silicone gums together with the oils defined above.
The alcoholic lotions contain, besides the organosiloxane bearing an ultraviolet-absorbing group, for example a lower alcohol containing 1 to 2 carbon atoms and preferably ethanol or isopropanol, or alternatively other alcohols such as alkylene glycols or glycol ethers.
When the compositions of the invention are emulsions, the fatty phase of the emulsions comprises either solely the screening organosiloxane or a mixture of the latter with other oils or waxes as defined above. The other phase of the emulsions comprises an aqueous medium.
The nonionic emulsions of the invention contain a nonionic emulsifier chosen, for example, from polyoxyethylenated fatty alcohols, polyoxyethylenated fatty acids, optionally polyoxyethylenated sorbitan esters, polyoxyethylenated or polyglycerolated alkylphenols, polyoxyethylenated or polyglycerolated fatty amides, and polyglycerolated fatty alcohols and alpha-diols; the number of moles of ethylene oxide preferably ranges from 2 to 50, and the number of glycerol groups preferably ranges from 2 to 30.
The cationic emulsions of the invention contain a cationic emulsifier chosen, for example, from quaternary ammonium halides such as di(C10-C30)alkyldimethylammonium halide, (C10-C30)alkyltrimethylammonium halide or (C10-C30)alkylbenzyldimethylammonium halide, and polyoxyethlenated quaternary ammonium salts containing from 2 to 30 mol of ethylene oxide. Distearyidimethyl-ammonium chloride and behenyltrimethylammonium chloride are more particularly used.
When the compositions of the invention are dispersions, they generally contain water and optionally an alcohol such as those mentioned above, a dispersion agent or an agent for suspending the screening silicone in water. Ammonium acrylate/acrylamide copolymers and crosslinked acrylic acid polymers may be mentioned, for example, as dispersion agents.
The compositions in accordance with the invention may also contain any other additive usually applied to keratin fibres and in particular the hair, such as, for example, dyes, surfactants, polymers, thickeners, conditioners, fragrances, preserving agents and softeners, as well as other screening agents,
The compositions in accordance with the invention may also be in the form of a spray or may be pressurized in aerosol devices.
The compositions of the invention intended to be applied to artificially coloured keratin fibres, and in particular human hair, are rinse-out products applied after dyeing, such as shampoos or conditioners, or alternatively leave-in products applied after dyeing, such as styling lotions, gels or foams, aerosol lacquers or sprays.
Artificially coloured keratin fibres, and in particular hair, are dyed using dyes that are used conventionally for the hair, such as oxidation dye precursors, by a dyeing process using an oxidizer such as aqueous hydrogen peroxide solution or air or alternatively by direct dyeing. Another possibility is to dye the keratin fibres in the presence of the screening organosiloxane. Another possibility is to apply a composition according to the invention based on the screening organosiloxane before dyeing the keratin fibres.
The subject of the present invention is also a cosmetic treatment process intended to protect the colour of dyed hair against the harmful effects UV radiation, and in particular solar radiation, comprising the step of applying, before or after dyeing the hair, an effective amount of a cosmetic or dermatological composition containing at least one organopolysiloxane compound as defined above.